1. Field of the Invention
The present invention relates to a chair seat cushion for a chair having a backrest and to the use of such a cushion.
The invention also relates to the seat cushion fitted to a chair, i.e. a chair fitted with said cushion.
In one embodiment, the invention relates to a chair seat cushion that can be placed on the seat of a chair having a backrest, to improve user seating comfort and particularly to enable the user to adjust his/her seating position in the chair.
The inventive chair seat cushion is intended to be used by people who are healthy with the exception of possible back pains, wherein the cushion is intended to be used to prevent the occurrence of back pains and to reduce or eliminate back pains of people who have or are prone to back troubles.
2. Description of the Related Art
Earlier techniques concerning contoured and structured chair seats are represented in U.S. Pat. No. 5,352,023, U.S. Pat. No. 4,726,624 and WO-A 94/10878, all of which relate to wheelchairs and more specifically to wheelchair seats that are designed for a different purpose to that intended by the invention, namely primarily to prevent a person seated in a wheelchair from sliding forwards on or from the chair seat, for instance in the event of an abrupt stop.
The wheelchair seat has a sunken rear part which receives the user's back to this end. The transition from the rear sunken part of the seat and the front raised part forms a barrier which functions to prevent the user from slipping forwards. A wheelchair-bound user will often lack the ability to feel or correct an unsuitable hip position in the wheelchair. The seat can be given the "right" length with respect to the horizontal distance between the user's back and his/her bent knees, by enabling the whole of the wheelchair seat to be moved longitudinally in relation to the wheelchair back rest. In order to enable the barrier to be positioned so that the user's back/hips lie more or less stably enclosed between the barrier and the wheelchair backrest, the use of narrow strap-like cushions which are supported across the seat and function to raise the front seat part have been proposed. These cushions can be arranged or removed to displace the effective position of the barrier along the seat.
When applying the known technique, it has been noted that roughly 75% of the user's body weight is transferred to the seat over an area of about 25 square centimeters (corresponding to the leg sitting area). In order to distribute this load over a wider area, it has been proposed to raise the aforesaid narrow barrier cushions to a level in which they project up over the level defined by the front part of the seat, thereby forming a pivot ridge which enables the weight of the user's thighs and legs to establish a pivotal moment around this ridge which tends to reduce the surface pressure on the user's back. The aforesaid technique also proposes the use of a liquid-filled cushion placed on the wheelchair seat to reduce the otherwise local high external load pressure on the user, or patient.